Artesia Tower, Mumbai, India – Vertical Post-Tensioning of a Reinforced Concrete Core Wall

Amitabh Kumar
Senior Vice President
Puranik Builders Limited, Mumbai

Artesia, a 240-meter residential tower, is under construction in downtown Mumbai. Residential flats have been stacked on the Arabian Sea-facing side for a spectacular view. Concomitantly, floor plates in the overall structure were reduced by 40 percent beyond 106.5 meters’ height. This design approach required the deliberate asymmetrical massing of the tower, which resulted in predominant tensile stresses in 35 percent of the total core-wall length. The reinforced-concrete core wall has been vertically post-tensioned up to a height of 150 meters, using 50-millimeter-diameter high-tensile (1030 MPa) threaded steel bars to neutralize tensile stresses—an innovative approach. To verify the effectiveness of the design, stresses and deflection of the core wall were computed and compared with alternative conventional designs without post-tensioning. The post-tension forces, coupled with wind load-induced forces, necessitate M80- and M70-grade concrete in the core wall. Post-tensioned bars, within polyethylene corrugated ducts, have been stressed at nine different levels across the height of the building, from the raft foundation to 150 meters’ height, and are grouted throughout.

The post-tensioning of the core wall increases construction time, which is compensated by using the Core-Preceding Construction Method for a faster slab construction cycle. All stressing levels have been carefully incorporated with the climbing formwork sequence. The thickness of the core wall, stress levels, and outrigger connections were carefully designed and planned. Post-tensioning enhances the core wall’s performance and durability over the life cycle of the tower by neutralizing tensile stresses and controlling inelastic creep deflection caused by asymmetrical massing.